Sample itinerary of Paris, questions etc

Could somebody provide me a sample itinerary of a trip to Paris? Or just ideas of what to do I'm currently stressing about all the logistics of things, and I want to get it out of the way so I can relax, and actually look forward to my trip! I'm currently in the process of planning my 2 week trip from 12 Sep - 26 Sep. I have a budget of about $2000 including room&board, food, activities, etc. That being said, just General questions: I see multiple things on getting from CDG to the city center, which is the preferred method? Where would I leave my bags during the day time since I will most likely be in a hostel, would I need to bring a padlock or something of the sorts? I'm looking at taking a 3-4 day trip to Brussels, or Amsterdam, would I be within budget to do this?

Currently I'm just stressing, and I want this to be a trip of a life time. Thanks all for your time!